The crystal structures of the ligand binding domains of the neurotrophin receptors trkA, trkB, and trkC have been solved and refined using synchrotron data collected at SSRL. The proteins are mis-folded, but a trivial modeling exercise produces the correct topology. The derived structures confirm the placement of a unique disulfide on the surface and allow discussion of Alanine-scanning data and ligand binding determinants. This will facilitate research into neuronal growth factors.